1. Field of the Invention
The invention relates to a lock structure for entry and exit passages, especially of nuclear installations, which lock structure includes a lock chamber having detectors associated therewith for surveillance of the passages and locking means for closing said lock chamber to prevent passage through the lock structure depending on the surveillance.
2. Description of the Prior Art
A lock structure consisting of a chamber with two doors which can be locked depending on test data obtained from sensors surveying the lock chamber is known. Because of dynamic measuring of the content of the chamber and since the content cannot be moved straight through the chamber as one door must always be closed, there have to be back-up areas in front of and after the detectors. It is therefore possible to deposit objects in a back-up area, that is, in front of the detector sensing section to prevent them from being detected until the opposite door is opened. If skillfully handled, they may then be taken out through the opposite door. Although this action will cause an alarm, the action itself cannot be prevented.
Furthermore, the concept permits only discontinuous individual operation which makes it practically impossible to handle a good number of people within a reasonable time especially since the size of the chamber must be kept as small as possible.
In order to prevent, under any circumstances, removal of radioactive materials from, or introduction of explosives into, a nuclear installation, an airlock structure for people consists of a rotatable cylinder having at least one lock chamber formed therein. The structure has detectors associated therewith such that, upon rotation of the cylinder in order to move the lock chamber between the entry and exit of the lock structure, the chamber is moved past the detectors thereby causing complete scanning of the lock chamber. Preferably, the rotatable cylinder is received in an opening of a wall structure of sufficient circumferential extent that the scanning of the chamber is completed before the chamber reaches the exit opening and locking means are provided which automatically lock the cylinder in position when activated by the detectors. The cylinder may consist for example of a solid body with vertical axis and having at least one radial cavity forming the chamber. There may be for example two chambers formed by a spider structure--like a normal revolving door wherein, however, only two opposite segments are open and the others are closed. In one embodiment, the revolving door consists of walls extending from the floor to the ceiling, the walls consisting of non-metallic material, preferably bullet-proof glass. Gamma detectors are used for the surveillance of the lock chamber. Additionally, metal detectors may be arranged around the lock chamber, the gamma detectors may be arranged in the axis of rotation of the revolving cylinder or they may be arranged in a frame structure around the lock chamber wherein one leg of such frame coincides with the axis of the revolving cylinder and another leg of the frame is arranged adjacent the circumference of the revolving cylinder. Metal detectors may be arranged at the entry and at the exit openings such that their effective ranges extend into the revolving cylinder area. They may even be arranged in the floor and/or the ceiling of the lock structure.
The locking means for the revolving cylinder consists of a mechanism which, in the preferred arrangement, includes a ratchet structure mounted either on the circumference of the revolving cylinder or formed as a cam-disc coaxial with, and connected to, the revolving cylinder such that rotation of the revolving cylinder in one direction is permitted, while rotation in the opposite direction is prevented in a stepwise fashion by automatically engaging spring-loaded or lockable latch members. There are preferably two such cam discs with latching cams spaced 90.degree. and effective to lock the respective discs in opposite directions of rotation with the locking surfaces of the cams and the respective latching members arranged about at the same positions. There are two latching members associated with one of the disks and spaced slightly less than 90.degree. by an angle of .epsilon..degree., the latches consisting of a mechanically operable latch and an automatically operating spring-biased latch, the other disc having only a mechanically operable latch associated therewith, the mechanically operable latches being lockable or releasable from outside the lock structure, for example by mechanical or electrical means.
The lock structure as lined out insures reliable sealing off of the containment area to be protected for reliable supervision. The lock structure is also easily operable and does not require any auxiliary operating energy. The simple locking mechanism safely locks the doors when activated by the sensors. Unrestricted passage is never possible. Every portion of the lock chamber is scanned before passage becomes possible which insures optimum surveillance. It is practically impossible to manipulate any detectable material or device in such a manner that it can be brought through the lock structure. In addition operating capacity of the lock structure is very high.